FLAT is a free 4D code library that allows you to perform quick lookups within external text data files. This is a helpful capability when your application is monitoring external data sources that are updated outside of your control. It can also be used instead of implementing static lookup tables and importing lookup data into your database.
(Source code is available)

Foundation 5 is a set of 4D v11 and greater components designed for use in new and existing database projects. A robust cross-platform shell is included for new database development. Full source code is included. For Macintosh and Windows.
(Source code is available)